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United States Patent |
5,748,270
|
Smith
|
May 5, 1998
|
LCD with electroluminescent backlighting
Abstract
An LCD assembly is disclosed. The LCD assembly includes a frame housing an
LCD material layered on an electroluminescent material layered on a
circuit board. One side of the circuit board includes elastomeric
connectors to connect to, respectively, the LCD material and the
electroluminescent material on the other side of the circuit board, a
third elastomeric connector attaches to the main circuit board of a
consumer product.
Inventors:
|
Smith; Dwight D. (Lynchburg, VA)
|
Assignee:
|
Ericsson, Inc. (Research Triangle Park, NC)
|
Appl. No.:
|
668472 |
Filed:
|
June 25, 1996 |
Current U.S. Class: |
349/69; 349/59; 349/149 |
Intern'l Class: |
G02F 001/133.3; G02F 001/134.5 |
Field of Search: |
349/58,60,69,59,149
|
References Cited
U.S. Patent Documents
5121234 | Jun., 1992 | Kucera | 349/69.
|
5146390 | Sep., 1992 | Wong | 349/60.
|
5243453 | Sep., 1993 | Kawaguchi et al. | 349/60.
|
Foreign Patent Documents |
404263220 | Sep., 1992 | JP | 349/60.
|
7333639 | Dec., 1995 | JP | 349/69.
|
Primary Examiner: Sikes; William L.
Assistant Examiner: Ngo; Julie
Attorney, Agent or Firm: Nixon & Vanderhye P.C.
Claims
What is claimed is:
1. An LCD assembly for connection to a main circuit board, comprising:
a frame, and
an LCD material layered on an electroluminescent material layered on a
driver circuit board, all within the frame, said driver circuit board
having two sides, one side having a main elastomeric conductive strip
electrically connecting the main circuit board, and the other side having
two additional elastomeric conductive strips electrically connected,
respectively, to said LCD material.
2. An LCD assembly according to claim 1, wherein said frame surrounds said
LCD material, electroluminescent material and said driver circuit board.
3. An LCD assembly according to claim 2, wherein said frame shields said
LCD material, said electroluminescent material and said driver circuit
board from RF signals.
4. An LCD assembly according to claim 1, wherein said electroluminescent
material is shorter in length than said LCD material so said additional
conductive strips bypass said electroluminescent material to electrically
connect said LCD material.
5. An LCD assembly according to claim 1, further including a front cover
attached to said frame.
6. An LCD assembly wherein said frame is tray-shaped.
7. An LCD assembly according to claim 1, further including a front cover
attached to said frame.
8. An LCD assembly according to claim 1 wherein the main circuit board
forms part of a consumer product and the front cover includes attachers
for physically attaching the front cover to the consumer product.
9. An LCD assembly for a product having a product circuit board comprising:
a frame, and
an LCD material layered on an electroluminescent material layered on a
driver circuit board, all within the frame, said driver circuit board
having two sides, one side having an elastomeric conductive strip at least
partially connecting the product circuit board of the product, and the
other side having an electrically conductive connection from said driver
circuit board to said LCD material and said electroluminescent material.
10. An LCD assembly according to claim 9, wherein said frame surrounds said
LCD material, electroluminescent material and said driver circuit board.
11. An LCD assembly according to claim 8, wherein said frame shields said
LCD material, said electroluminescent material and said driver circuit
board from RF signals.
12. An LCD assembly according to claim 9, further including drivers on said
circuit board electrically connected to said LCD material and said
electroluminescent material.
Description
FIELD OF THE INVENTION
This invention relates to LCDs, and more particularly, to LCD assemblies
with electroluminescent backlighting.
BACKGROUND OF THE INVENTION
Liquid Crystal Displays (LCDs) are well-known and popular display devices
used in many electronic consumer products, such as pagers, calculators,
watches, television screens, etc. In some devices, such as in pagers, LCDs
can be subject to some physical abuse and wear. For this reason, LCDs are
usually employed behind a protective cover to prevent the LCD from impact
and exposure.
As is by now well known, the LCDs work by applying electronic signals to a
matrix of conductors connected to the LCD structure. By applying signals
to particular x- and y- coordinates on the LCD matrix, different portions
of the display are darkened, thus producing symbols, numbers, letters or
characters to the viewer. To control how the signals are applied to the
particular coordinates, the LCDs are electronically driven by an LCD
driver, usually located on a driver board. The driver board is part of the
total LCD assembly, which typically includes the LCD, the driver board,
and a lens over the LCD, all housed in the protective cover.
The LCD must, of course, be in electrical communication with the driver
board in order to receive the x- and y- matrix signals. To accomplish
this, prior LCD assemblies employed solder connections between the LCD and
the driver board. Alternatively, LCD assemblies used jumpers, such as pin
and socket connections to get the matrix signals from the driver board to
the LCD. The driver board, in turn, was also connected to the remaining
circuitry of the consumer product (the pager, calculator, etc.) with
solder or jumpers in order to receive, among other signals, its control
signals and electronic power.
The LCD is usually physically attached to the driver board, which is
physically attached to the protective cover. The cover and/or the driver
board are then attached to the product to make the LCD assembly a device
that is integral with the product as a whole.
LCD assemblies are usually back-lit by LEDs or lightguides located on the
main circuit board of the consumer product. LCD assemblies are usually
custom products designed to accommodate the particular back-lighting
arrangement provided by the consumer product to which the LCD will
ultimately be assembled.
Another form of display device is an electroluminescent display.
Electroluminescent displays typically include a layer of
electroluminescent material that emits light when subjected to a high
electric field. Electroluminescent displays are driven by drivers that
control the electrical stimulation of the electroluminescent material.
When an LCD or an electroluminescent display are assembled with their
driver boards into a display assembly, electrical connections are made
from the LCD to its driver or from the electroluminescent material to its
driver. Additional electrical connections must be made from the driver
board to the main circuitry of the consumer product to which the display
is attached. Solder leads are usually designed onto the consumer product
circuit board to accept the electrical connection from the display
assembly. The assembly of such a display device involves intricate
maneuvering to complete the complicated coordination of physical and
electrical connections, both within the display device and between the
display device and the main circuit board. Improvements in manufacturing
efficiency are always desirable in producing such display assemblies.
SUMMARY OF THE INVENTION
The present invention provides an improved LCD structure and significantly
improves the efficiency of manufacturing LCD devices by eliminating solder
connections between the LCD and its drivers, and also between the LCD
assembly and the main circuit board. The present invention achieves these
efficiencies with an LCD assembly that can be made relatively large, has
its own backlighting, and provides shielding from external radio
components. According to one embodiment, an electroluminescent material is
sandwiched between an LCD material and a driver board, with conductive
tape providing a solderless connection for power to the panel. Elastomeric
connections are also made between the main circuit board and the LCD
assembly.
This LCD assembly is manufactured by layering various components on top of
each other and then connecting them all physically and electrically by
compressing and holding the layers together with screws. The screws secure
the layers for physical integrity. Also, the compression from the screws
causes elastomeric conductive connectors to compress within the layers to
create the necessary electrical conductivity between the layers.
The manufacturing operation is greatly simplified. The LCD assembly is
placed into and retained by a front cover. The frame is metal and provides
a structure within which the LCD material, the electroluminescent
material, and the driver board are arranged. The frame provides extra
protection for the LCD assembly against impact damage and shields the LCD
and electroluminescent display drivers from other radio circuits.
All electrical connections within the above assembly are made by
compressive silicone conductive strips. No solder is required, nor is any
access to the boards required to complete electrical conductivity. When
the layers are inserted into the frame, in the layers described above, and
the driver board and frame are screwed down to the front cover, the
compression of the components causes the compressive silicone conductive
strips to complete the necessary electrical connections automatically as
the screws are tightened down.
Finally, an additional elastomeric connection provides electrical
conductivity between the LCD assembly and the main circuit board of the
consumer product.
The present invention vastly improves manufacturing time and increases the
ease of assembling LCD devices for consumer products by eliminating
soldering and jumpering between the component layers and eliminating
soldering and jumpering between the LCD assembly and the main circuit
board of the consumer product. In addition, the present invention allows a
more closely enveloping (and hence more protective) frame to be used
around the various components of the LCD assembly since the frame does not
need to maintain access to the components and boards in order to complete
electrical connections between the various components. That is, since
electrical connections occur automatically as the layers are screwed down
to each other, access is not required to make the electrical connection
and the frame can then be designed without access requirements in mind.
In addition, the present LCD assembly can now be used as a universal
component in a variety of different consumer products since the LCD
assembly includes its own backlighting and thus does not need to be
customized to accommodate the particular backlighting provided by the
consumer product.
BRIEF DESCRIPTION OF THE DRAWINGS
The purpose and advantages gained by the present invention will be
understood by careful study of the following detailed description of the
presently preferred embodiment with particular reference to the
accompanying drawings.
FIG. 1 is an exploded perspective view of an example embodiment of the
present invention;
FIG. 2 is another exploded perspective view of the embodiment of FIG. 1;
FIG. 3 is an exploded perspective view of a detailed example embodiment of
the present invention;
FIG. 4 is another exploded perspective view of the embodiment of FIG. 3;
FIG. 5 is a cut-away orthogonal view of the embodiment of FIG. 3; and
FIG. 6 is a detail cut-away of one section of the embodiment shown in FIG.
5.
DETAILED DESCRIPTION OF THE DRAWINGS
An example embodiment of an LCD application 10 employing the present
invention is shown in FIGS. 1 and 2. The LCD assembly 10 includes a number
of parts layered one upon another. A front cover 11 is made of plastic or
metal and houses within it a gasket 12, a frame 13 in contact with the
gasket 12 sandwiches an LCD material 15, an electroluminescent lighting
material 16 behind the LCD material 15, and an electronic board 18. The
assembly snaps into six snaps 19 in the front cover 11 and then the board
21 is screwed to the front cover 11.
The operation of the LCD material 15 and the electroluminescent material 16
are generally known to require appropriate electronic drivers 20, which
are located on the electronics board 18. Traditionally, the drivers 20
were electrically connected to the LCD material 15 and electroluminescent
material 16 by solder or jumpers. Unfortunately, during assembly, using
solders or jumpers to make these electrical connections requires intricate
skill to coordinate the electrical connection of the drivers 20 to the LCD
15 and electroluminescent material 16 at the same time the board 18 is
being physically assembled with the LCD 15 and electroluminescent material
16 in the frame 13 and front cover 11.
To solve this problem, the present invention uses elastomeric connectors
17B made of compressible silicone conductive strips to make contact with
the LCD 15 as the board 18 is placed into the frame 13. The use of
compressible silicone conductive strips for these connections eliminates
soldering, and is reliable down to 0.05.OMEGA. contact resistance. In
addition, the frame 13 is designed for maximum impact protection by
closely enveloping the LCD 15, material 16, etc. Conductive tape 22 is
used to make contact with the electroluminescent material 16 and the board
18.
In the embodiment of FIGS. 1 and 2, when the frame 13 is physically
assembled into the front cover 11, it sandwiches the LCD 15, and
electroluminescent material 16 between the board 18 such that, when the
board 21 is screwed down to the front cover 11, the two elastomeric
connectors 17B on the ends of board 18 are compressed, respectively,
against the LCD 15 to make the necessary electrical connections. Material
16 is slightly shorter than LCD 15 to permit the elastomeric connectors
17B to bypass the material 16 and connect directly to the LCD 15.
During assembly, the frame 13 snaps into the snap 19 on the front cover 11.
Then, board 21 is screwed to front 11 to secure the sandwich into one
integral assembly. The frame 13 is optionally separated from the circuit
board 21 by shock pad 25. The frame acts, in part, as a shield for the LCD
15, electroluminescent material 16, and board 18 from stray radio
frequency signals.
Electroluminescent material 16 provides background lighting built right
into the LCD assembly, thus eliminating any LED or lightguide requirements
on the consumer product circuit board to which the LCD assembly ultimately
attaches. The electroluminescent lighting drivers are mounted onto the
board 18 next to the LCD drivers.
The elastomeric connectors are made of alternate layers of conductive and
non-conductive silicone or, alternatively, of silicone wrapped with thin
gold plated loops. These connections are commercially available from such
known companies as Elastomeric Technologies and Ampaflex.
Board 18 is a standard printed circuit board that makes electrical
connection between the drivers 20 and the elastomeric connector 17B such
that the elastomeric connectors, when connected with the LCD 15, make the
appropriate electrical connections between the drivers 20 and the LCD 15.
In this way, the drivers 20 control the operation of the LCD 15 in
generally known fashion.
When the LCD assembly 10 is fully assembled and the board 18 is screwed
down between the frame 13 and front cover 11, the exposed side of the
board 18 (FIG. 1) contains another elastomeric connector 17A. This
connector 17A in receptacle 17C electrically connects to the elastomeric
connectors 17B and also electrically connects to the main circuit board 21
of the consumer product to which the LCD assembly 10 is operative. From
the main circuit board, the elastomeric connector 17A receives power and
control signals and delivers them to the drivers 20, the LCD material 15
and electroluminescent material 16. This assembly method and apparatus
eliminates LED and light guide requirements on the main circuit board yet
is easier to manufacture than prior assembly methods.
As can be seen from the assembly drawings of FIGS. 1 and 2, the LCD
assembly 10 in accordance with this embodiment of the present invention
can be rapidly assembled, with all electrical and physical connections
made simply and easily in one step by screwing the frame 13 and board 18
to the front cover 11.
FIGS. 3-6 show an additional embodiment of the present invention. FIGS. 3
and 4 are exploded perspective views of the embodiment described and shown
in FIGS. 3-6. FIGS. 3 and 4 are views of the LCD module 110, with FIG. 3
viewed from the top and FIG. 4 viewed from the bottom. In addition, FIG. 4
is rotated 180.degree. compared to FIG. 3.
In the embodiment of FIGS. 3 and 4, frame 113 is in the form of a metal
tray, within which the LCD 115, electroluminescent material 116, board
118, and elastomeric connector material 117A are layered. The elastomeric
connector 117A extends from the frame 113 through openings 141 to contact
the main circuit board of the consumer product to which the LCD assembly
110 is to be used.
An optional spacer and shockpad 160 may be used to space the main printed
circuit board of the consumer product from the frame 113 at an end of the
frame 113 opposite the elastomeric connector 117A.
As shown in FIG. 4, printed circuit board 118 includes LCD drivers 151 and
electroluminescent material drivers and support chips 150.
As in the embodiment of FIGS. 1 and 2, the embodiment of FIGS. 3 and 4
includes electroluminescent material 116 to backlight the LCD 115. Board
118 includes all drivers and other circuitry required to operate the
electroluminescent panel 116 and LCD 115. Electrical connections can be
made from board 118 to electroluminescent panel 116 and LCD 115 by
additional elastomeric connectors (not shown) such as described with
respect to FIGS. 1 and 2, or alternatively can be provided by flexible
ribbon.
Other than the as shown differences in the Figures, the embodiment of FIGS.
3 and 4 is functionally similar to the embodiment of FIGS. 1 and 2.
FIG. 5 is an orthogonal view of an LCD 115, electroluminescent material
116, elastomeric connector 117A, board 118, and frame 113. As shown in
FIG. 5, the LCD material 115 lays on top of the electroluminescent
material 116, which in turns lays on top of the board 118. Frame 113
surrounds these materials and holds them in place within its protective
metal surrounding. The elastomeric connector 117A is held in a receptacle
117B on the board 118, as shown in FIG. 6. FIG. 6 is a detailed cutaway of
the right-portion of the structure shown in FIG. 5. As shown in FIG. 6,
the elastomeric connector 117A extends from the board 118 and faces
outward from the assembly 110 (compare to FIG. 1) to connect to the main
circuit board (not shown) of the consumer product to which the LCD
assembly 110 is used. A punch tab 140, which is part of the frame 113,
supports the board 118 on the main circuit board of the consumer product
and snaps the LCD into the front cover. With reference to FIG. 3, the
front cover 11 (not shown) would attach at the top of the exploded view to
sandwich materials 115, 116, and board 118 into frame 113.
In the presently preferred embodiment, the frame 113 is composed of
nickel-silver. The electroluminescent material 116 is a strip of
approximately 0.3 mm thickness. The elastomeric connectors are layered
conductive and non-conductive silicone with a 10-20% compression and a
contact resistance of 0.05.OMEGA..
While the invention has been described in connection with what is presently
considered to be the most practical and preferred embodiment, it is to be
understood that the invention is not to be limited to the disclosed
embodiment, but on the contrary, is intended to cover various
modifications and equivalent arrangements included within the spirit and
scope of the appended claims.
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